The present invention relates to a device for controlling the opening/closing operation of an electrical switchgear, such as a circuit breaker or a disconnector or a recloser or the like, and a control method related.
More specifically, the present invention relates to a device, which allows controlling the opening/closing operation of an electric switchgear, using a real time sensor-less control system.
Devices for controlling the opening/closing operation of an electric switchgear are well known in the state of the art.
An example of this kind of control devices, particularly useful for medium and high voltage applications (i.e. for a voltage range higher than 1 KV), is disclosed in the European patent application N° 98204083.4, filed in the name of the same applicant, the description of which is to be understood as included herein, as reference.
In the mentioned patent application, it is disclosed a device for controlling the opening/closing operation of an electric switchgear, which is able to adjust in real time the control parameters in input to an actuator. In this way, it is possible to obtain a desired law of motion for movable parts of the electric switchgear, which the mentioned actuator operates.
In order to process the control signals necessary for achieving this aim, a control unit, which is included in the control device, is used. This control unit is needed to know in real time the position of the movable parts of the electric switchgear.
This is obtained, in the embodiments described in the mentioned patent application, using one or more feedback signal, which can provide the control unit with information, directly or indirectly related to the position of the movable parts of the electric switchgear.
This information can be provided in a direct manner, for example, with one or more feedback signals that can be sent by position and/or velocity and/or acceleration sensors, suitably placed in predefined points of the kinematic chain, which connects the actuator to the movable parts of the switchgear. As it can be easily understood, this approach has the main drawback of requiring the placement of dedicated sensors for generating feedback signals for providing the control unit, in a direct or indirect manner, with information related to the position of movable parts the switchgear.
Alternatively, this information can be provided, in an indirect manner, avoiding the use of position sensors. In fact, in this case, feedback signals, related the control parameters of the actuator, are generated by current/voltage sensors and subsequently sent to the control unit of the control device. In this way, the position of the movable parts can be calculated by the control unit. Also this solution, even if achieving the aims for which it has been conceived, has some drawbacks, such as the need of complex electronics (and related setting-up procedures) for generating the control signals necessary for adjusting in real time the control parameters in input to the actuator.